Ultra high frequency electronic device



ATTOPNEY A; E. BOWEN ULTRA-HIGH FREQUNCY ELECTRONIC DEVICE Filed July 3,1942.

' Feb. 25, 1947.

Patented Feb. 25, 1947 ULTRA HIGH FREQUENCY ELECTRONIC DEVICE Arnold E.Bowen, Red Bank, N. J., assignor to Bell Telephone Laboratories,Incorporated, New York, N. Y., a corporation of New York ApplicationJuly 3, 1942, Serial No. 449,581

Claims. (01. 315-6) This invention relates to systems employingresonators and resonant cavities so shaped and constructed as to besuitable for reaction with an electron stream to enable anelectromagnetic field which may be set up in the resonator or resonantcavity to induce a variation in some characteristic property of theelectron stream,'or, to permit an interchange of energy between theresonator and the electron stream.

In particular the resonator may be in the shape of a short section of anelliptical cylinder, hollow inside and closed oil by parallel planesheets. A wave guide may be connected to the resonator at a focal pointor elsewhere according to the amount of impedance to be provided at thejunction point.

The invention is applicable generally toamplifiers, oscillators,modulators, detectors and the like particularly at ultra-highfrequencies, wherever it is desired to effect direct interaction betweenan electromagnetic field and an electron stream.

This application is a continuation-in-part of my copending applicationSerial No. 387,432, filed April 8, 1941, Patent 2,408,409, grantedOctober 1, 1946.

The combination of two elliptical cavity resonators with electroniccoupling between one pair of respective focal points in the resonatorsand with a two-directional coupling means connected between another pairof corresponding points in the two resonators, not necessarily focalpoints, disclosed herein, is claimed in my copending application SerialNo. 621,365 filed October 9, 1945, assigned to the sameassignee as thepresent application.

An oscillator and harmonic generator formed by an elliptical cavityresonator and a circular number of illustrative examples, while itsscope is indicated by the appended claims.

In the drawing: Figs. 1 and 2 show a sectional view and a plan orelevational view, respectively, of an oscillator employing ellipticalresonators and a stream of electrons;

Figs. 3 and 4 show similar views of another-embodiment, employingelliptical resonators and a pair of electron streams, one stream througheach of the foci of the ellipse; and

Figs. 5 and 6 show similar views of an amplifier or a frequencymultiplying arrangement employ ing an elliptical resonator and acircular resonator.

In Figs. 1 and 2 there are shown two substantially elliptical resonators31 and 38 with focal points indicated at 39 and 40. The resonators maybe built with walls of copper or other suitable material, the innersurfaces, at least, being pref-' erabfy highly conductive. Eachresonator may be viewed as comprising a short section of ellipticalcylinder closed off by parallel, plane end walls. Aperturesare cutthrough the plane walls of each ellipse at focus 39 and the resonatorsare joined by a cylindrical conductive tube 4| covering the apertures.Additionalapertures are cut through the resonator walls preferably nearthe periphery at a point remote from focus 39 and the resonators arejoined at this point by a cylindrical conductive. tube 42. Coaxiallywith tube 42 is placed a rod of conductive material 43 which is held inplace by insulating'hermetic seals at 44 and 45. A hollow conductivecylinder 6 is fastened over an aperture 5 in the left-hand end wall ofthe resonator 31 as viewed in Fig. 1. The tube 6 is joined by means of asuitable hermetic seal 1 to an insulating envelope 8 of glass or othersuitable material. Within the envelope 8 are provided the usual ele:ments of an electron gun or beam projector 46 of any suitable typecomprising, for example, a cathode 9, and an accelerating electrode 10cooperating with the cylinder 6 to direct an electron beam through theapertures in the resonators 31 and 38 aligned with the axis of tube 4|.A pair of gaps 41 and 4,8 are constituted, as indicated, in the path ofthe beam. The gap 48 is defined by the edges of the aperture 5 and theedges of an aperture in the right-hand end wall of the resonator 31 atthe entrance to the tube 4|. The gap 4! is defined by'the edges of anaperture in the I left-hand end wall of the resonator 38 and theright-hand end wall of that-resonator. Batteries H, H and I3 or othersuitable sources may be provided, respectively, for heating the cathode9, energizing the-accelerating electrode HI and applying an acceleratingpotential to the conductive system comprising the resonators 31 and 38,and the tubes 4|, 42 and 6. The tube 4| serves not only as a passage forthe electron stream but also as an electromagnetic shield defining adrift'space within which the electron bunching action hereinafterdescribed may be effectuated free from fluctuating electromagneticfields.

In the operation of the arrangement of Figs. 1 and -2, the electronscomprising the electron j the system in oscillation.

stream from the gun 48 are subjectedat the gap 48 to interaction withany electromagnetic field which may exist in the resonator 31 and at thegap 41 with any such field that may exist in the resonator 38. Anaccidental irregularity in the.

a charge density of the electron stream will suflice I to set up anelectromagnetic wave in the resonaftor 38 as the irregularity passesacross the gap cavity of the resonator 38 and converges again at Thewave thus set up spreads through the 1 the focus 40, inducing current inthe conductor I F 43 where the latter crosses the cavity. An inducedwave travels over the coaxial transmission f line comprising the tube 42and the conductor 43 into the resonator 31. A wave is induced in thelatter resonator which wave in the course of propagation converges uponthe gap 48. Each elec- 1 tron in its passage across the gap 48 eithertakes energy from or gives energy to the electromagnetic field in theresonator 31, depending upon the phase of the field during its transitof the gap. The velocities of the electrons are varied in accordancewith this energy interchange. After leaving the gap 48, thevelocity-varied electrons pass through the tube 4| where a grouping orbunching effect takes place, those electrons which have lost energy andhave; as a conse- 1 quence, been slowed down being overtaken by otherelectrons which entering later, have gained 1 energy and have speetledup. Consequently, at a point some distance to the right of the gap 48, Ithe electrons are traveling inmore or less welldefined groups. Uponreaching the gap 41 the bunches of electrons may, if the length of the 1tube 4| and the initial speed of the electrons have I been adjustedcorrectly, cross the gap 41 in opposition to the high frequencyelectromagnetic field, I thus contributing energy to the field, and ingreater amounts than are absorbed by the thinly 1 distributed electronswhich may cross the gap 41 during the unfavorable phase of-the highfrequency field- The net energy contributed by the 1 electron stream tothe field tends to sustain and build up the original wave and thus tomaintain It may be further noted 1 described, upon first arriving at theap 48 and there initiating an electron group in the electron j stream,is, in effect, reflected back through the resonator 31 and coaxial line42, 43 into the resonator 3'8 and to -gap 41. ,Ifthe velocity of theelectrons in the beam -is adjusted so that the electron bunch reachesthe gap 4'!- at the same time the reflected wave arrives there, or anintegral 1 number of cycles later, a fresh supply of energy is given tothe wave and the oscillation is maintained. The adjustment in this casewill also satisfy the condition for oscillation specified in thepreceding paragraph.

insulating seal I92. I lected at the right-hand end wall of theresonator 38 and returned to the battery l3.

- The type of construction shown in Figs. 1 and 2 I accommodates amagnetizing coil .49 which may 1 be wound around the cylinder 4| andused to im- 1 prove the collimation and focusing of the electron stream.Energy may be extracted from the system by any suitable means, such as acoupling loop I98 connected .across a coaxial transmission line |9|. Thevacuum chamber will include the envelope 8, the resonators 31, 38 andthe tubes 6,

that the wave above tubes 4|, 42. In order to secure the proper phaserelations for the waves, the electron streams are oppositely directed.The resonators .31 and '38 are shown as in Fi 1. An electron gunrepresented schematically by a cathode 50 is arranged to direct a streamof electrons across the gap 48, down the interior of the tube 4| andacross the gap 41 to a collector plate 5|. A second electron gunrepresented by a cathode 52 is located at the focal point 48 andarranged to direct an electron beamacross a velocity-varying gap 54,through the interior of the tube 42 and across an energy extracting gap55 to a collector -53. The axial rod 43 and. the seals 44 and 45 are notused in this embodiment. A second magnetizing coil 58 may beplacedaround the outside of the tube 42.

4|, 42 and the closure may be completed with an The spent electrons arecol- Figs. 3 and 4 show an arrangement similar to j that shown in Figs.1 and 2 except that two electron streams are employed, one in each ofthe In the operation of the system shown in Figs. 3 and 4, anelectromagnetic disturbance occurring in the ga 41 serves to set up awave which is focused upon the gap 54 and there effects a velocityvariation of the electron stream from the cathode 52. 52 in crossing thegap 55 a brief time later sets up a wave which is focused upon themodulating gap 48 and produces a velocity variation .of the electronstream from the cathode 50. This velocity-varied stream a. short timelater arrives at the gap 4'! and sets up a new disturbance. If-thetransit times of the two electron streams through the tubes 4| and 42,respectively, are properly adjusted, the waves originating at the gaps41 and 55, respectively, will be in proper phase to, maintain theoscillations. Viewed as a feedback means,

either electron stream constitutes an electronic feedback asdistinguished fromthe coaxial line feedback of the system of Figs. 1 and2.

The construction shown in Figs. 1 and 3 will be observed to require aminimum of insulating material and practically none in the spacecontaining the high frequency field.

Figs. 5 and 6 show an application of the invention to an amplifier or afrequency multiplier and also combinethe use of elliptical and circularresonators. An input coaxial line with inner conductor 8| and outerconductor 82 intersect-s an elliptical resonator 83. The right-handportion of the coaxial line beyond'the resonator 83 is adjustable fortuning purposes by means of a piston 84 slidable ever the conductor 8|.An electron gun represented schematically at 85 is arranged to send anelectron stream across a gap 86 in the resonator 83, through a drifttube 81 and across a gap 88 to-a collectorfl89. The gap 88 is situatedat the center of a circular resonator 90. The plan view is shown in Fig.6.

' In the operation of the system of Figs. 5 and 6 a wave to be amplifiedor to have its frequency multiplied is brought into the system throughthe coaxial line 8|, 82. The incoming wave sets up waves in theelliptical resonator 83 which waves are focused upon the gap 86 wherevelocity variation of the electron stream from the electron gun 85 iseffected. After passing through the drift .tube 81, the electron stream,with its electrons The velocity-varied stream from the cathode auaaastage of frequency multiplication, the resonator 90 may be designed withsufllciently small dimensions to resonate a desired harmonic of theinput wave. If amplification alone is desired the resonator ispreferably designed to resonate at the frequency of the wave impressedupon the system by the coaxial line ll. 32.

The impedance presented to the line the resonator 83 is dependent uponthe point of connection of the line to the resonator. By properselection of this point an impedance match may usually be secured. Thepoint may be found by calculation or trial and will not, in general, beat the focus of the ellipse.

What is claimed is:

1. An oscillator comprising two spaced-hollow elliptical resonators,means adjacent focal points of said resonators to project an electronstream successively through one of said resonators at a focal pointthereof and into the other resonator at a focal point thereof, a shieldsurrounding the portion of the path of said electron stream between saidresonators for shielding said electron stream from fluctuatingelectromagnetic fields in the space between said resonators, andfeedback coupling means extending between the interiors of saidresonators at another pair of respective focal points.

2. An electronic oscillator comprising a Pair elliptical resonators andmeans connecting corresponding focal points of each resonatortogetherand including means for producing a p ir of electron streams,each of the respective streams when in operation forming a substantiallyunidirectional coupling between a focal point in one of said resonatorsand a focal point in the second of said resonators..

3. An electronic oscillator comprising a pair of spaced ellipticalcylindrical resonators and means connecting corresponding focal pointsof each resonator together and including means for producing a pair ofelectron streams, each of the respective streams when in operationforming a substantially unidirectional coupling between a focal point inone of said resonators and a focal point in the second of saidresonators.

4. An oscillator comprising two spaced fiat, hollow, ellipticalresonators, means adjacent focal points of said resonators to project anelectron stream successively through one of said resoject an electronstream successively through one of said resonators at a focal pointthereof into the other resonator at a focal point thereof, saidprojecting mean-s being oppositely directed with respect to the order inwhich the electron stream enters the respective resonators.

ARNOLD E. BOWEN.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PA Number Name .Date

2,281,935 Hansen et a1. May 5, 1942 2,304,186 Litton .Dec. 8, 19422,318,106 Ryan May 4, 1943 2,317,140 Gibson Apr. 20, 1943 2,338,237Fremlin Jan. 4, 1944 2,281,550 Barrow May 5, 1942 2,241,119 Dallenbach.4 May 6, 1941 2,284,405 McArthur May 26, 19-42

